Electric incandescent bulb



Dec. 29, 1942. w. s. PEARSON 2,306,559

ELECTRIC INCANDESCENT BULB Filed Sept. 19', 1941 fiE- M44 mu 6". P544? so.

Patented Dec. 29, 1942 UNITED 'STATES PATENT OFFICE 2,306,559 ELECTRIC INCANDESCENT BULB William S. Pearson, Park Ridge, Ill. Application September 19, 1941, Serial No. 411,476 12 Claims. (Cl. 176-40) This invention is directed to improvements in electric incandescent bulbs.

In the past, in order that illumination be obtained from a circuit having a given voltage, it has beennecessary that an incandescent bulb having a filament calibrated to that particular circuit and that particular voltage be used. This is necessary because when a filament so calibrated is connected in a circuit having a lower voltage than that forwhich it is calibrated, it will give much less illumination than that desired. On the other hand if a bulb having a filament calibrated for a given voltage is placed in a circuit having a higher voltage than that calibrated for, the filament will either immediately burn out or will burn for a very limited period of time before deteriorating.

In order that the above disadvantages may be obviated and as an important object of the invention there is provided herein an improved incandescent bulb which will adapt itself to various voltages.

Another object of the invention is to provide an incandescent lamp having an improved filament unit which will give the desired degree of illumination at a lower voltage and will accommodate itself to a higher voltage to give the same efficiency of illumination and at the same time will not burn out or deteriorate prematurely.

Still another object of the invention is to provide an improved incandescent bulb having a segmented filament.

A further object of the invention is to provide an improved incandescent bulb with a plurality of filaments which are so arranged that each is progressively brought into the circuit as the bulb is subjected to progressively higher voltages.

As is well known to those skilled in the art, the life of a filament is proportional to the temperatures at which it is operated and accordingly there is provided herein, means for controlling these temperatures whereby the life of the filament is greatly increased.

To the end that the above objects may be attained there is provided herein an incandescent bulb having an improved filament including a plurality of segments, each additional segment being provided with a shunt circuit connected in parallel therewith, the shunt circuit including a fusible conductor adapted to rupture from the excess heat radiated or from the increase in the temperature of the filament, due to the added voltage impressed thereon. As the voltage increases, the respective fusible elements rupture and thus break the shunt circuit with the result that additional filament segments are brought into the circuit as the voltage increases.

Many other objects and advantages of the invention will become apparent from the following description and the accompanying drawing in which:

Figure 1 represents a cross-sectional view of an incandescent bulb utilizing one embodiment of the invention.

Figure 2 is a cross-sectional view taken on the line II-II of Figure 1.

Figure 3 is an enlarged fragmentary view of a portion of the filament unit shown in Figure 1.

Figure 4 is an enlarged fragmentary view of a modified form of a filament unit embodying the invention. 1

Figure 5 is a cross-sectional view taken on the line VV of Figure 4.

Figure 6 is an enlarged fragmentary view of a further modified form of a filament unit embodying the invention.

Figure 7 is a top plan view of the structure shown in Figures 1 and 3.

Figure 8 is an enlarged fragmentary view of another modified form of a filament unit embodying the invention; and

Figure 9 is a diagram of a circuit embodying the invention.

It is to be understood that the modifications shown herein are for illustrative purposes only and may be changed or modified without departing from the spirit and scope of the invention, as set forth in the appended claims.

While the invention herein may of course be adapted to any use in which circuits of varying voltages are encountered, it is found to be particularly advantageous when used in incandescent bulbs which are intended to be connected in auxiliary household circuits such as those from which doorbells, chimes, or sign and number lights are operated. In such circuits, standardization is not ordinarily found and as a result, a wide variety of voltages is encountered. frenerally speaking the variety in the voltage value of such circuits ranges anywhere from 8 to 25 volts. Manufacturers of illuminated household numbers and the like have in the past found it necessary to carry in stock bulbs calibrated for various voltages and it is necessary for the customer to specify the particular voltage desired in order that the proper bulb be provided for the circuit in question.

As will be seen presently there is provided herein an incandescent bulb having a fiiament unit which is so constructed and arranged that it adapts itself to a wide range of voltages with the result that standard bulb of a single style may be provided to accommodate the varying voltages found in these household circuits.

Referring to the drawing and particularly to Figure 1, a representative bulb here shown includes a glass globe portion I having a restricted neck portion II which is fitted in and secured to a threaded socket I2 by means of suitable cementitious insulating material I3.

The restricted portion II. of the bulb is formed to provide an inwardly extending, upstanding insulating bead I4 which serves as the supporting base for the filament unit to be described hereafter.

While a varying number of filament segments may be provided there is shown herein a unit including four segments, I5, I6, I! and I8. The filament comprising these sections is suitably connected as at 24 at its ends to the upper ends of lead conductors I9 and 20, the bases being embedded in the glass insulating bead I4.

The filament segments are further supported by means of dummy leads 2 I, 22 and 23' the upper ends of which engage the filament between the various segments and the lower ends of which are also embedded in the insulating bead I4.

The lower end of the lead conductor I9 is connected with a conductor 25 which in turn is embedded in the cementitious base I 3 and terminates in a contact button 25 at the base of the incandescent bulb, while the lead conductor 20 has its lower end connected with a conductor 21 which likewise is embedded in the cementitious base I3, the extremity of which is in contact with the threaded socket I2 as at 28.

In operating the filament unit shown herein it is necessary that only one of the filament segments be incorporated in the circuit when the bulb is connected in a low voltage circuit and to this end there is provided herein a shunt circuit around the segments I8, I1 and I8 whereby the latter are used only upon higher voltages and the segment I is instantly available for use at low voltages.

As shown in Figure 1 these shunt circuits include the upper ends of leads 2|, 22, 23 and as shown at 23, 38, 3I and 32 respectively. The

leads are connected by a conductor having sections 33, 34 and 35, this conductor being formed from a readily fusible material having a low melting point for purposes to be described presently.

As previously explained the dummy leads 2|, 22 6 and 23 are connected with the filament between the various segments thereof and consequently the upper ends of the leads provide connections with the filament which afiord individual shunt circuits for each segment I6, I1 and I8.

As will be seen from the foregoing, when the bulb shown in Figure 1 is connected in a circuit the current will flow through the lead conductor l9 and the filament I5 lighting the same whereupon it will fiow through the shunt circuit which is of relatively lower resistance than the filament segments I8, I! and I8. Thus the current will fiow through the conductors 29, 33, 34, 35 and the lower portion of lead conductor 20.

So long as a current of reduced voltage passes through the filament unit, the segment I5 will be illuminated and the conductors 29, 33, 34, 35 and 20 will serve to cut-segments I 6, I1 and I8 out of the circuit. If, however, the voltage is increased a predetermined amount the increased radiated and conducted heat (as ascertained by the predetermined resistances of segments l5, I6 and I1 and I8 or by the added current in the shunt itself, or both) radiated upon the adjacent fusible conductor 33 will cause the latter to melt and thus cut the segment I5 into the circuit to be illuminated. Similarly, by progressive increases in the voltages passing through the filament unit, fusible conductors 34 and 35 will be progressively melted to cut in segments I1 and I8 until, at the maximum voltage for which the unit is calibrated, the entire filament will be in the circuit to give the desired illumination with out prematurely burning out.

The conductors 33, 34 and 35 may be secured in the filament in any suitable manner as by crimping the leads therearound as shown at 36 in Figure 2.

Thus it will be seen that without manipulation of any kind and in fact without any attention from the user, the filament unit embodying the present invention will automatically adapt itself to the voltage of the circuit in which it is incorporated.

It will be understood that the filament here described may be made from any suitable material such as tungsten or the like and that the fusible conductors 33, 34 and 35 may be made from tin, zinc, lead or other suitable conductors or alloys of the same preferably having a relatively low melting point.

While the various parts of the filament unit may be constructed and arranged with many different electrical dimensions to accommodate many and various voltage ranges and to cut in the filament segments at varying predetermined voltage value, an example of a satisfactory unit, accommodating circuits from 8 to 25 volts is substantially as follows: In a unit calibrated at .15 amp. the segments I5, I8, I! and I8 may be constructed to ofler resistances of 80 ohms, 20 ohms. 40 ohms and ohms respectively at operating temperatures. The fusible conductors 33, 34 and 35 are, in such a unit, of such dimensions and constituency that they will successively melt when a current of 10 to 13 volts, 13 to 18 volts and over 18 volts, respectively is passed through the unit. Experimentation with bulbs of the character here shown reveals that there is little or no residual heat when the bulb is disconnected from the circuit. In other words, the action upon the filament and the fusible material is instantaneous and thus the bulb instantaneously accommodates itself to the voltage impressed upon the circuit.

It will be understood that the conductor 33 is melted by excessive heat radiated from segment I5 and by an increase in its own temperature while conductors 34 and 35 are likewise melted by excessive heat from the preceding filaments which are in the circuit in advance of the segment being shunted by the respective conductor, the excessive heat in each case being the result of a rise in the voltage impressed upon the bulb. When applied to the highest voltage as designated, all of the shunts will melt out substantially instantaneously due to the intense heat created as above described.

By varying the electrical dimension of the various elements and by choice of fusible conductors having predetermined melting points it will be seen that one skilled in the art may construct a filament unit to accommodate any predetermined voltage range and wherein the various segments may be incorporated in the circuit as currents of an infinite number of predetermined voltages are impressed upon the filament unit. Furthermore, by increasing the number of filament segments, the availability of a bulb for a wider variety of circuits may be increased accordingly.

In the embodiment shown in Figures 4 and 5 the filament is similarly divided up into segments l5a, l6a, Fla, and Na and is similarly supported by leads Ha, Ha, 22a, 23a. and 20a, the leads 19a and 20a constituting the conductor leads for the filament while the leads Ha, 22a and 23a are dummy leads as provided in Figure 1. In this embodiment of the invention the shunting of the current around the filaments [6a, Ha and No is similarly accomplished by parallel shunting circuits. However, the circuits in this instance comprise low resistance fusible metal sheath segments or coatings lGb, I'Ib and Nb respectively which cover the filament wire as shown in Figure 5.

It is to be understood that the application of the sheath to the filament segments may be accomplished in any of the known manners such as drawing, dipping or the application of a brazing paste. The various elements of the filament unit may be calibrated by one skilled in the art to obtain the desired results as is explained in connection with Figure 1.

From the foregoing it will be seen that as the current enters the lead conductor l9a it passes through the filament segment l5a to illuminate the same and thence passes through the sheath segments lib, Nb and Nb into the conductor 20a. If, however, the bulb in which this modified filament unit is incorporated, should be connected with a circuit having a higher voltage, then the sheath l'lb will become overheated due to radiated and conducted heat from filament segment l5a, and will melt with the result that the filament segment no will be exposed and illuminated. Similarly the sheaths 11b and lab are melted and fall from the respective filament segments as the bulb is connected in circuits of increasing voltage.

The above described modified filament unit is highly desirable in that the manufacturing step required to clamp or crimp the fusible element into a parallel circuit with the respective segments as shown at 36 in Figures 1 and 2, is eliminated.

In Figure 6 a further modified form of filament embodying the invention is disclosed. In this construction, the fusible element having sections 31, 38 and 39 is positioned within the coils of the filament and crimped into the upper end of the beads Me, 220, 23c and 200 along with the intermediate portions of the filament between filament segments I60, I and 180. With such a construction, it will be seen that the unused portion of the filament is supported to a certain degree and that the fusible element is incorporated into the assembly with a minimum of manufacturing operations.

In the construction shown in Figure 8 the filament unit is assembled in a manner very similar to that shown in Figures 1, 2 and 3 with the exception, however, that the fusible element including sections 33e, 34c and -35e is crimped to the respective leads in a manner to be disposed angularly with respect to the filament. From the drawing it will be seen that the section 33c of the fusibl element which first ruptures upon a rise in the voltage impressed upon the circuit,

is positioned closest to the filament while the sections 34c and 35e are positioned progressively further away therefrom.

With such a construction it will be understood that the rupturing effect of the heat radiated from the filament segments is utilized to a greater extent in that those sections of the fusible link which are to rupture first are closer to the filament and therefore subjected to heat of a much more intense degreethan those sections which are to deteriorate late.

By reference to Figure 9 the circuit followed by the current in the filament unit shown in Figure 1 will be clearly understood. The current entering the lead conductor I! will flow through the segment l5 thence through the conductor 29 and fusible elements 33, 34 and 35 to the lead conductor 20. However, if the bulb is inserted in circuits having increasingly high voltages the fusible conductors 33, 34 and 35 will be progressively melted until such a time as the current flows through the conductor IS, the filament segments l5, l6, l1 and I8 illuminating the same, and thence through stitutes the upper end of the lead conductor 20.

It will be understood that while various particular circuits have been shown and described herein, many variations thereof may be devised to incorporate the advantages of the present invention which include, among others, the pro-. vision of a filament unit having a plurality of filament sections, certain of said sections being so arranged that they will not initially be subjected to current thus enabling efiicient illumination to be obtained from others of the sections when the filament unit is incorporated in a low voltage circuit, which sections however will automatically be incorporated in the circuit at such times as the filament unit is subjected to higher voltages. Under such circumstances it will be seen that the invention herein provides an incandescent bulb which functions efiiciently to give the desired illumination when incorporated in a low voltage circuit and which at the same time gives the desired illumination when incorporated in circuits of higher voltages without the filament deteriorating prematurely.

If desired, the fusible conductors shown may be constructed to cut the various segments into the circuit at progressively increasing voltages by giving them different current carrying capacities. Thus each will have a progressively higher melting point and a current of higher voltage will be required to deteriorate each successive conductor.

I claim as my invention:

1. In a filament unit for an incandescent bulb accommodating itself to varying voltages, a pair of lead conductors, a segmented filament connected therebetween for illumination when subjected to a predetermined voltage, a shunt circuit associated with said filament, said circuit being arranged to connect an intermediate point of said filament with one of said lead conductors and including a fusible conductor formed to afford illumination of the portion of said filament around which the shunt circuit was connected as a current of predetermined higher voltage passes through the filament unit.

2. In a filament unit for an incandescent bulb accommodating itself to varying voltages, lead conductors and filament segments connected in series therebetween, said segments being calibrated to afford varying resistance, and a shunt circuit connected in parallel with certain of said segments and including fusible conductors formed the conductor 32 which conto rupture progressively as currents of higher voltage pass through the filament unit.

3. In a filament unit for an incandescent bulb, lead conductors and segmented filament of relatively high resistance connected between said conductors, a shunt circuit of relatively low resistance connected in parallel with a part of said filament, said circuit including a conductor formed to fuse when subjected to predetermined voltages lower than that would normally disintegrate the filament.

4. In an incandescent'bulb which may be emciently illuminated by varying voltages, a filament unit including lead conductors, filament segments connected therebetween and shunt circuits connected in parallel with certain of said segments, each of said circuits including a fusible conductor formedv to rupture when the filament unit is subjected to a predetermined higher voltage thereby to progressively incorporate the remaining filament segments in the circuit to be illuminated as said unit is subjected to progressively higher voltages.

5. In an incandescent bulb which may be illuminated by varying voltages, a filament unit including lead conductors, filament segments connected therebetween, each of said filament segments having different resistance and shunt circuits connected in parallel with certain of said segments, said circuits each including a fusible conductor, said fusible conductor being formed to progressively rupture by heat conducted and radiated from the preceding segment as the filament is subjected to progressively higher voltages.

6. In an incandescent bulb, for use in circuits of varying voltages, a filament unit including a pair of lead conductors, a filament having a plurality of segments connected therebetween, dummy leads connecting with said filament between said segments, shunt circuits for certain of said segments including fusible conductors connected between respective leads and in parallel with the respective segments.

7. In an incandescent bulb for use in circuits of varying voltages, a filament unit including a pair of lead conductors, filament having a plurality of segments of differing resistance connected therebetween, dummy leads connecting with said filament between said segments, shunt circuits for certain of said segments including fusible conductors connectedbetween respective leads in parallel with the respective segment, said fusible conductors being formed to pro gressively rupture under 'the influence of the heat generated by the segments to expose successive segments to current as the voltage passing therethrough is increased.

8. In an incandescent bulb for use in circuits of varying voltages, a filament unit including a pair of lead conductors, a segmented filament connected therebetween, a shunt circuit for a portion of said filament, said circuit including a coating of fusible conducting material on said filament, said coating extending from a point intermediate the length thereof to one of said. lead conductors and being formed to rupture and expose the filament covered thereby to current upon a rise in the voltage passing through the filament, said filament being of such construction that the fused material can be liberated therefrom.

9. In an incandescent bulb for use in circuits of varying voltages, a filament unit including a pair of lead conductors, a filament including a plurality of segments having varying resistance connected therebetween, means for shunting certain of said segments to render them inoperative at predetermined low voltages, said means including 'a sheath of fusible conducting material on certain of said segments, and connecting with one of said conductors, said sheaths being formed to rupture progressively as the voltage passing through the bulb is increased to increase the tempertaure of the filament, said filament being of such construction that the fuse material can be liberated therefrom.

10. In an incandescent bulb for use in circuits of varying voltages, a filament unit including a pair of lead conductors, a filament including a plurality of segments of varying resistance connected therebetween, a shunt circuit connected in parallel with certain of said segments, said circuits each including a fusible conductor, said fusible conductors being connected in series with each other and with one of said lead conductors.

11. In an incandescent bulb for use in circuits of varying voltages, a filament unit including a pair of lead conductors, a filament having a plurality of segments of differing resistance connected therebetween, dummy leads connected with said filament between said segments, shunt circuits for certain of said segments including fusible conductors connected between respective leads parallel with the respective segments, said fusible conductors being formed to progressively rupture under the influence of heat generated and radiated by the segments to expose successive segments to current as the voltage passing therethrough is increased, said conductors being connected between said leads and being disposed progressively at a relatively greater distance from the respective segments.

12. In an incandescent bulb for use in circuits of varying voltages, a coiled filament unit including a pair of lead conductors, a coiled filament including a plurality .of segments of varying resistance connected therebetween, a shunt circuit connected in parallel with each of said segments, said circuits each including a fusible conductor, said fusible conductors being connected-in series with each other and with one of the lead conductors and being disposed within the coil of said filament, said filament being of such construction that the fuse material can be liberated therefrom.

WILLIAM S. PEARSON. 

